The present invention fits in the field of compounds and compositions useful as conglomerate building materials, and more specifically in the sector of water retaining additives for conglomerate building materials such as special mortar and gypsum.
In the last few years, filled conglomerate building material compositions are being used more and more in replacement of conglomerate building materials, since they have noteworthy advantages as to their placement conditions, such as workability, initial degree of adherence and water retaining power during kneading, etc., as well as in their final properties, such as for example their qualities of adherence, resistance and finish.
These filled conglomerate building material compositions include additives, additional to the components of traditional conglomerate building materials, that provide the above mentioned advantageous properties.
Within the different types of filled conglomerate building materials, there are some whose final properties require the use of a thickening agent and water retaining agent. Among these materials are special mortar and gypsum that are used in very different applications such as the bonding among enclosures or supports with different ceramic materials, facade coverings, repairing and engobing.
Gypsum and special mortar, such as glue mortar, conventionally comprise a series of additives, such as for example water retaining agents. A water retaining agent is a product that due to its molecular structure and to its surface properties bonds to the water by means of xe2x80x9cweak bondsxe2x80x9d and retains the water in the matrix of the conglomerates during the setting and hardening process. The rheology in the paste that is formed is improved. The water retaining additives conventionally used for conglomerate building materials such as special mortar and gypsum, are based on cellulose-like derivatives, no alternative thereto being known up until the present.
European patent application EP-A-0773198 describes a thickening system that contains at least a cellulose-like ether, a starch ether, thickening components and a layer silicate such as sepiolite, bentonite and other clay, that correspond to such an additive on the market.
Cellulose-like derivatives provide, based on their thickening effects, greater consistency to conglomerate building materials aside from increasing their water retaining and adherence capacities. Nonetheless, cellulose-like derivatives have the disadvantage of being relatively expensive and therefore conglomerate building materials such as traditional mortar and gypsum, without or with less than the necessary doses of such derivatives, are still being used, despite their poorer qualities with respect to filled compositions, for many uses when the use of a sufficiently filled conglomerate composition would really be more appropriate.
U.S. Pat. No. 5,637,144 describes a substitutive composition of asbestos that comprises water, water retaining agents and finely divided clay, especially bentonite, while U.S. Pat. No. 4,028,127 describes a mixture of cement comprised of gypsum with the product resulted from reacting a guar hydroxyalkyl ether with glyoxal that is useful to cover up cracks and holes in surfaces. None of the compositions described in the above mentioned U.S. patents can be applied as mortar or gypsum.
An object of the present invention is to overcome the inconveniences of conventional gypsum and special mortar, that comprise cellulose-like derivatives, by means of the replacement of such derivatives by a new additive that allows achievement of placement and final qualities at least similar to said conventional filled compositions and in turn allow a reduction of the total cost of the final compositions.
Another object of the invention is to make available a new additive that improves at least one of the placement and final qualities with respect to conventional gypsum and special mortar.
Another object of the invention is to make available a new additive for gypsum, special mortar, such as glue mortar, single layer.
The present invention also has the object of filled compositions comprising special mortar and gypsum that contain the additive as well as the use of the new additive in special mortar and gypsum.